Insertion of Shape Memory Alloy Wire with 3D Printed Thermoplastic Polyurethane Structure for Flexural Application

The shape memory alloy (SMA) wire actuator is desirable to modify the structure properties and shape morphing ability particularly for the aircraft wing application. However, SMA wire embedded directly into a matrix system caused mismatch in coefficient of thermal expansion (CTE) which further led to delamination and structure failure issues. Thus, a soft material that integrated effectively with SMA actuator to achieve shape changing while resisting the external load is required. In this work, SMA wire is inserted through the gaps in corrugated 3D printed thermoplastic polyurethane (TPU) elastomeric structure to analyze the geometrical factors and its flexure performance. The flexure test results indicated that TPU with inactive SMA insertion has sustained higher flexure load with 21% increase in both flexure modulus and maximum load. However, activated SMA wire insertion demonstrated opposite behavior by increasing bending moment. Flexure test on fixed-fixed single SMA wire further supported the above finding. Moreover, SMA inserted into top eccentric from neutral axis of TPU sample has achieved highest flexure modulus and maximum load followed by at bottom and neutral axis. Thus, this design approach is presented to signify the structural integrity of 3D printed TPU with SMA and flexure property modification through SMA eccentric position.